If you’re running Rawhide, and you update and dnf isn’t there any more, don’t panic! This is intentional and expected. It’s part of the decision to revert the Change that intended to make dnf5 the default for F39.
For fresh F39 installs and upgrades from F38 to F39, everything will be smooth, but for folks who were running Rawhide during the time we had dnf5 obsoleting dnf, it’s a bit more bumpy. You’ll have dnf5 installed and dnf not installed, then you’ll update, and get a build of dnf5 that no longer provides /usr/bin/dnf (because we don’t want dnf5 to be the default any more).
Don’t panic! To get dnf back, you should just need to do this:
dnf5 --best install 'dnf < 5'
Just dnf5 install dnf may actually be enough after the next Rawhide compose completes, but the above should be safe. You can then do dnf remove dnf5 if you want to not have two dnfs, or just keep it (you can still run it as dnf5 in this case).